Basket-shaped catheter with improved distal hub

ABSTRACT

This disclosure is directed to a catheter having a basket-shaped electrode assembly with a high electrode density. The basket-shaped electrode assembly may have a plurality of spines, such as up to twelve, each with a plurality of electrodes, such as up to sixteen. The distal ends of the plurality of spines are joined at a distal hub, all of which are fashioned from a single piece of superelastic material.

FIELD OF THE PRESENT DISCLOSURE

This invention relates to electrophysiologic (EP) catheters, inparticular, EP catheters for mapping and/or ablation in the heart.

BACKGROUND

Electrophysiology catheters are commonly-used for mapping electricalactivity in the heart. Various electrode designs are known for differentpurposes. In particular, catheters having basket-shaped electrode arraysare known and described, for example, in U.S. Pat. Nos. 5,772,590,6,748,255 and 6,973,340, the entire disclosures of each of which areincorporated herein by reference.

Basket catheters typically have an elongated catheter body and abasket-shaped electrode assembly mounted at the distal end of thecatheter body. The basket assembly has proximal and distal ends andcomprises a plurality of spines connected at their proximal and distalends. Each spine comprises at least one electrode. The basket assemblyhas an expanded arrangement wherein the spines bow radially outwardlyand a collapsed arrangement wherein the spines are arranged generallyalong the axis of the catheter body.

It is desirable that a basket assembly be capable of detecting in as fewbeats as possible, including a single beat, as much of the electricalfunction of the region in which the electrode assembly is deployed, suchas the left or right atrium as possible. By implementing a greaternumber of electrodes in the electrode assembly, correspondingly greaterand more complete coverage of the region may be obtained. Further, theincreased number of electrodes may reduce or eliminate the need toreposition the electrode assembly to access all of the desired area inthe region. Often, increasing the number of electrodes corresponds withan increase in the number of spines or other structures that support theelectrodes. These spines are joined at a distal end by a central hub. Asthe device is deployed, a number of the distal electrodes may be put ina position that they are not in contact with the tissue. Additionally,the increase in the number of spines generally relates to an increase inthe length and diameter of an elongated distal hub that is used toconnect the spines. Devices that have a larger distal hub may be harderto deliver and deploy within a patient and may increase the risk oftrauma to the tissue. Another problem with prior art distal hubs is thatthe movement from a delivery state to a deployed state causes stress inthe structure as it transitions. This stress may cause undesirabledamage to the device. As such, there is a need for a basket-shapedelectrode assembly having an increased electrode density whilemaintaining a sufficiently minimized distal hub diameter and length thatwill improve the deployment and electrode contact within a chamber of apatient's heart and decrease the stress to the material as the devicetransitions to the deployed configuration. The techniques of thisdisclosure satisfy this and other needs as described in the followingmaterials.

SUMMARY

The present disclosure is directed to a catheter including an elongatedcatheter body extending along a longitudinal axis, the elongatedcatheter body having a proximal end and a distal end, a flexible wireassembly positioned at the distal end of the elongated catheter bodyformed from a single piece of shape memory material, the flexible wireassembly having a plurality of flexible wires, each flexible wire havinga proximal end and a distal end and a distal hub, the distal hubextending from the distal ends of at least a portion of the plurality offlexible wires and a plurality of spines formed from the plurality offlexible wires. The catheter further includes a plurality of electrodesand cabling attached to each spine, the plurality of electrodes andcabling having a corresponding plurality of wires coiled on a core andcovered by a sheath such that each electrode is attached through thesheath to one of the plurality of wires, such that the catheter has oneoperational state wherein the spines bow radially outwardly and anotheroperational state wherein the spines are arranged generally along alongitudinal axis of the catheter body.

In one aspect, the distal hub further includes at least onestress-relieving edge.

In one aspect, at least a portion of the shape memory material of thestress-relieving edge comprises a first thickness at a distal end andtapering to a second thickness at the distal end of the flexible wire.

In one aspect, the stress-relieving edge further includes a radius ofcurvature, the radius of curvature directed toward an inner diameter ofthe distal hub.

In one aspect, the plurality of flexible wires further includes a bridgeportion, the bridge portion connecting the distal end of the flexiblewires to the distal hub.

In one aspect, the distal ends of two adjacent flexible wires form abridge portion, the bridge portion connecting the flexible wires to thedistal hub. The bridge portion may have a linear or sinusoid shape.

In one aspect, the distal hub is a waveform, the wave form furtherincludes a plurality of U-shaped indentations or sinusoidal shapedindentations, wherein each indentation is placed between adjacentflexible wires. The indentations define a gap, the gap having a firstdistance when in the delivery configuration and a second distance whenin the deployed configuration.

In one aspect, the distal hub is a continuous ribbon shaped waveform,the wave form includes a plurality of distal indentations, where eachdistal indentation is placed between adjacent flexible wires and extendsdistally from the distal ends of the flexible wires. The ribbon shapeddistal hub has a plurality of distal indentations that are distallyoriented and a plurality of proximal indentations that are proximallyoriented, wherein the distal indentations and proximal indentationsalternate and are evenly spaced around a circumference of the distalhub.

In one aspect, the distal hub has a first stress relieving edge and asecond stress relieving edge, the first stress relieving edge has awaveform shape on a distal end of the distal hub, and the second stressrelieving edge has an arched shape on a proximal edge of the distal hub,the distal hub further includes at least two distal projections, whereinthe distal projections are evenly distributed around a circumference ofthe distal hub.

In one aspect, a catheter is made by the steps of forming an elongatecatheter body, forming a flexible wire assembly from a single piece ofshape memory material, the flexible wire assembly having a plurality offlexible wires joined at a distal hub and forming a stress-relievingedge onto a distal end of the distal hub at a location opposite of theplurality of flexible wires. The catheter is further made by heating theflexible wire assembly to heat set a basket-shaped arrangement,connecting a plurality of electrodes and cabling to each of theplurality of flexible wires to form a basket-shaped electrode assemblyand connecting the basket shaped electrode assembly to a distal end ofthe elongate catheter body.

In one aspect, the single piece of shape memory material is a nitinolalloy tube.

In one aspect, the stress relieving edge may be a bridge portionconnecting the flexible wires to the distal hub, or a continuouswaveform, the continuous waveform having a plurality of indentations ormay include a plurality of distal projections.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages will become apparent from the followingand more particular description of the preferred embodiments of thedisclosure, as illustrated in the accompanying drawings, and in whichlike referenced characters generally refer to the same parts or elementsthroughout the views, and in which:

FIG. 1 is a top plan view of a catheter of the present invention,according to one embodiment.

FIG. 2 is a schematic view of the basket-shaped electrode assembly ofFIG. 1 deployed in the left atrium.

FIG. 3 is a schematic view of a basket-shaped electrode assembly,according to one embodiment.

FIG. 4 is a schematic view of a flexible wire assembly of thebasket-shaped electrode assembly of FIG. 3.

FIG. 5 is a schematic view of an expanded flexible wire assembly of thebasket-shaped electrode assembly, according to one embodiment.

FIG. 6 is a schematic view of a distal end of a flexible wire assemblyin a delivery configuration, according to one embodiment.

FIG. 7 is a schematic view of a distal end of a flexible wire assemblyin a deployed configuration, according to one embodiment.

FIG. 8a is a schematic view of a distal end of a flexible wire assemblyin a delivery configuration, according to one embodiment.

FIGS. 8b and 8c are cross sections of the distal hub of the flexiblewire assembly of FIG. 8a , according to one embodiment.

FIG. 9 is a schematic view of a portion of a distal end of a flexiblewire assembly in a deployed configuration, according to one embodiment.

FIG. 10 is a schematic view of a portion of a distal end of a flexiblewire assembly in a deployed configuration, according to one embodiment.

FIG. 11 is a schematic view of a portion of a distal end of a flexiblewire assembly in a deployed configuration, according to one embodiment.

FIGS. 12a and 12b are schematic views of a portion of a distal end of aflexible wire assembly in a delivery configuration and deployedconfiguration, respectively, according to one embodiment.

FIGS. 13a and 13b are schematic views of a portion of a distal end of aflexible wire assembly in a delivery configuration and deployedconfiguration, respectively, according to one embodiment.

FIG. 14 is a schematic view of a portion of a distal end of a flexiblewire assembly in a deployed configuration, according to one embodiment.

FIG. 15 is a schematic view of a portion of a distal end of a flexiblewire assembly in a deployed configuration, according to one embodiment.

FIG. 16A is a top view of a cabling of a spine of a basket-shapedelectrode assembly with part(s) broken away, according to oneembodiment.

FIG. 16B is an end cross-sectional view of the cabling of FIG. 16A.

FIG. 16C is a side view of the cabling of FIG. 16A, with part(s) brokenaway.

FIG. 17 is a schematic illustration of an invasive medical procedureusing a basket-shaped electrode assembly, according to one embodiment.

DETAILED DESCRIPTION

At the outset, it is to be understood that this disclosure is notlimited to particularly exemplified materials, architectures, routines,methods or structures as such may vary. Thus, although a number of suchoptions, similar or equivalent to those described herein, can be used inthe practice or embodiments of this disclosure, the preferred materialsand methods are described herein.

It is also to be understood that the terminology used herein is for thepurpose of describing particular embodiments of this disclosure only andis not intended to be limiting.

The detailed description set forth below in connection with the appendeddrawings is intended as a description of exemplary embodiments of thepresent disclosure and is not intended to represent the only exemplaryembodiments in which the present disclosure can be practiced. The term“exemplary” used throughout this description means “serving as anexample, instance, or illustration,” and should not necessarily beconstrued as preferred or advantageous over other exemplary embodiments.The detailed description includes specific details for the purpose ofproviding a thorough understanding of the exemplary embodiments of thespecification. It will be apparent to those skilled in the art that theexemplary embodiments of the specification may be practiced withoutthese specific details. In some instances, well known structures anddevices are shown in block diagram form in order to avoid obscuring thenovelty of the exemplary embodiments presented herein.

For purposes of convenience and clarity only, directional terms, such astop, bottom, left, right, up, down, over, above, below, beneath, rear,back, and front, may be used with respect to the accompanying drawings.These and similar directional terms should not be construed to limit thescope of the disclosure in any manner.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one having ordinaryskill in the art to which the disclosure pertains.

Finally, as used in this specification and the appended claims, thesingular forms “a, “an” and “the” include plural referents unless thecontent clearly dictates otherwise.

Certain types of electrical activity within a heart chamber are notcyclical. Examples include arterial flutter or arterial fibrillation,and ventricular tachycardia originating in scars in the wall of theventricle that have resulted from infarcts. Such electrical activity israndom from beat to beat. To analyze or ‘map’ this type of electricalactivity, it is desirable to obtain the ‘picture’ as quickly aspossible, such as within one heartbeat. In other words, all the pointsof the map or picture may be obtained simultaneously within one-tenth ofa second. According to the techniques of this disclosure, abasket-shaped electrode assembly having a high electrode density withimproved electrode-to-tissue contact may be used to accurately map thiselectrical activity.

As shown in FIG. 1, the catheter 10 comprises an elongated catheter body12 having proximal and distal ends and a control handle 14 at theproximal end of the catheter body, with a basket-shaped electrodeassembly 16 having a plurality of spines 18, each carrying multipleelectrodes 20, mounted at the distal end of the catheter body 12. Thecatheter body 12 comprises an elongated tubular construction having asingle, axial or central lumen 26, but can optionally have multiplelumens if desired. To enable accurate mapping of electrical signals, forexample to detect most or substantially all of the electrical functionof the right or left atrium in as little as a single heartbeat, it maybe desirable to provide an array of electrodes with a relatively highdensity. As such, the number of spines 18 employed may be six, eight,ten, twelve or any other suitable number. The distal ends of spines 18are joined together at a distal hub 22. Distal hub 22 is a generallycircular and flat structure to allow for more of the electrodes 20 tocontact the tissue to be mapped. Spines 18 may be evenly or unevenlydistributed radially about distal hub 22. Further, each spine 18 mayinclude multiple electrodes 20, such as at least eight and up toapproximately 16 electrodes per spine. Similarly, the electrodes may beevenly distributed along the spine or may be skewed proximally,centrally or distally to facilitate analysis of the measured electricalsignals.

The catheter body 12 is flexible, i.e., bendable, but substantiallynon-compressible along its length. The catheter body 12 can be of anysuitable construction and made of any suitable material. Oneconstruction comprises an outer wall made of polyurethane or PEBAX®(polyether block amide). The outer wall comprises an imbedded braidedmesh of stainless steel or the like to increase torsional stiffness ofthe catheter body 12 so that, when the control handle 14 is rotated, thedistal end of the catheter body will rotate in a corresponding manner.The outer diameter of the catheter body 12 is not critical, butgenerally should be as small as possible and may be no more than about10 french depending on the desired application. In one aspect, theoverall diameter of the catheter body 12 may relate to the number ofelectrodes 20 implemented by basket-shaped electrode assembly 16 inorder to accommodate the associated electrical leads. For example, atwelve-spine design with each spine carrying sixteen electrodes for atotal of 192 electrodes, a ten-spine design with each spine carryingsixteen electrodes for a total of 160 electrodes and an eight-spinedesign with each spine carrying sixteen electrodes for a total of 128electrodes may utilize up to a 10.0 french catheter body. Likewise thethickness of the outer wall is not critical, but may be thin enough sothat the central lumen can accommodate a puller wire, lead wires, sensorcables and any other wires, cables or tubes. If desired, the innersurface of the outer wall is lined with a stiffening tube (not shown) toprovide improved torsional stability. An example of a catheter bodyconstruction suitable for use in connection with the present inventionis described and depicted in U.S. Pat. No. 6,064,905, the entiredisclosure of which is incorporated herein by reference.

Spines 18 include a shape memory material, as described below, thatfacilitates assuming an expanded arrangement. As shown in FIG. 2, whenthe basket-shaped electrode assembly 16 assumes the expandedconfiguration, spines 18 bow outwards into contact or closer proximitywith the walls of the chamber in which it has been deployed, such as theleft atrium.

In one aspect, an electrophysiologist may introduce a guiding sheath,guidewire and dilator into the patient, as is generally known in theart. As an example, a suitable guiding sheath for use in connection withthe inventive catheter is a 10 french DiRex™ Guiding Sheath(commercially available from BARD, Murray Hill, N.J.). The guidewire isinserted, the dilator is removed, and the catheter is introduced throughthe guiding sheath whereby the guidewire lumen 26 permits the catheterto pass over the guidewire. In one exemplary procedure as depicted inFIG. 2, the catheter is first introduced to the right atrium (RA) viathe inferior vena cava (IVC), where it passes through the septum (S) inorder to reach the left atrium (LA).

As will be appreciated, the guiding sheath covers the spines 18 of thebasket-shaped electrode assembly 16 in a collapsed position so that theentire catheter can be passed through the patient's vasculature to thedesired location. Once the distal end of the catheter reaches thedesired location, e.g., the left atrium, the guiding sheath is withdrawnto expose the basket-shaped electrode assembly 16. Upon withdrawal ofthe guiding sheath, the shape memory material of the basket-shapedelectrode assembly radially expands the device within the chamber. Withthe basket-shaped electrode assembly 16 radially expanded, the ringelectrodes 20 contact atrial tissue. As recognized by one skilled in theart, the basket-shaped electrode assembly 16 may be fully or partiallyexpanded, straight or deflected, in a variety of configurationsdepending on the configuration of the region of the heart being mapped.

When the basket-shaped electrode assembly 16 is expanded, theelectrophysiologist may map local activation time and/or ablate usingelectrodes 20, which can guide the electrophysiologist in diagnosing andproviding therapy to the patient. The catheter may include one or morereference ring electrodes mounted on the catheter body and/or one ormore reference electrodes may be placed outside the body of the patient.By using the catheter with the multiple electrodes on the basket-shapedelectrode assembly, the electrophysiologist can obtain a true anatomy ofa cavernous region of the heart, including an atrium, allowing a morerapid mapping of the region.

As used herein, the term “basket-shaped” in describing the electrodeassembly 16 is not limited to the depicted configuration, but caninclude other designs, such as spherical or egg-shaped designs, thatinclude a plurality of expandable arms or spines connected, directly orindirectly, at their proximal and distal ends. In one aspect, differentsized basket-shaped electrode assemblies may be employed depending onthe patient's anatomy to provide a close fit to the area of the patientbeing investigated, such as the right or left atria.

A detailed view of one embodiment of the basket-shaped electrodeassembly 16 is shown in FIG. 3, featuring a total of twelve spines 18,each carrying sixteen electrodes 20. As noted above, in otherembodiments, different numbers of spines 18 and/or electrodes 20 may beemployed, each of which may be evenly or unevenly distributed asdesired. The distal ends of the spines 18 are joined at distal hub 22.Correspondingly, the proximal ends of the spines 18 may be secured tothe distal end of the catheter body 12. Lumen 26 may be used as aguidewire lumen. In some embodiments, lumen 26 may also be used tosupply a suitable irrigation fluid, such as heparinized saline, to thebasket-shaped electrode assembly 16. A fitting (not shown) in thecontrol handle 14 may be provided to conduct irrigation fluid from asuitable source or pump into the lumen 26.

Each spine 18 may comprise a flexible wire 28 with a non-conductivecovering 30 on which one or more of the ring electrodes 20 are mounted.In an embodiment, the flexible wires 28 may be formed from a shapememory material to facilitate the transition between expanded andcollapsed arrangements and the non-conductive coverings 30 may eachcomprise a biocompatible plastic tubing, such as polyurethane orpolyimide tubing. A plurality of flexible wires 28 may be joined to forma flexible wire assembly 29.

FIGS. 4 and 5 illustrate one embodiment of a flexible wire assembly 29.Flexible wire assembly 29 comprises a plurality of flexible wires 28.The distal ends of each flexible wire 28 are joined at distal hub 22. Inone embodiment, flexible wire assembly 29 is composed of Nitinol, anickel-titanium alloy. As illustrated in FIG. 4, in one embodiment,flexible wire assembly 29 is formed from a single cylindrical tube ofnitinol. In this embodiment, the nitinol tube has an outer diameter of2.59 mm (0.102 inch) and an inner diameter of 2.18 mm (0.086 inch). Inone example, the outer diameter is no greater than 10 french.Additionally, in an embodiment, the nitinol tube has a length between 1mm (0.039 inch) and 20 mm (0.79 inch) that is sufficient to form thespines. One of ordinary skill in the art will appreciate that the lengthof the spines may vary and will correspond to the size of the chamberinto which the device is deployed.

As mentioned above, the flexible wire assembly 29 is formed from asingle tube. In one embodiment the nitinol tube is cut using standardcutting techniques such as laser cutting or etching. In anotherembodiment, an appropriate drill may be used to trace a pattern into anitinol tube and then a laser may be used to complete the pattern in thenitinol tube. Other known methods of forming the nitinol tube into theflexible wire assembly 29 may be used. Using an appropriate laser, theflexible wires 28 and distal hub 22 are cut from the tube as a singleunit. The individual flexible wires 28 are cut into the tube leavingmaterial that will form the distal hub 22. In one embodiment, the heightof the distal hub 22 is the same dimension as the thickness of thenitinol tube from which the assembly is cut. In this embodiment, theheight of the distal hub 22 is reduced as compared to the prior art.During use, this reduction in height translates to a distal hub having areduced dimension when in the deployed configuration. The reduceddimension of the distal hub 22 may allow more of the electrodes in closeproximity to the distal hub 22 to come in contact with the chamber,making the mapping of the chamber faster and more accurate.

The process of forming the tube into the flexible wire assembly 29 alsoincludes forming at least one stress-relieving edge 31 on hub 22. Thestress-relieving edge 31 is a shaped edge to facilitate movement of thebasket-shaped electrode assembly 16 from a delivery arrangement to adeployed arrangement. As illustrated in FIGS. 4 and 5, the stressrelieving edge 31 comprises a scalloped shaped edge on the distal end ofthe flexible wire assembly 29. The formation of this edge reduces theamount of material of the distal hub. This reduction of material allowsfor the spines to expand into the basket-shape with a lesser amount ofstress on the distal hub 22. It will be appreciated that as the flexiblewires 28 expand into the basket-shape, the shaped edge 31 of the distalend of the distal hub moves, or rotates, inwardly to become an innerdiameter of the deployed distal hub 22. In so doing, the deployed innerdiameter of the distal hub 22 reduces in size as the basket-shapeddevice is formed. Thus, the removal of this material in forming thedistal hub 22 will reduce the stress and strain on the hub as it ismoved from the delivery arrangement to the deployed arrangement. In anadditional step in forming the distal hub 22, any sharp edges on thescalloped edge may be smoothed in order to prevent tissue damage duringuse. Other geometries for this stress-relieving edge are discussed inmore detail below in relation to FIG. 8a to FIG. 15 and may include, forexample, a wave form edge, a tabbed edge, or a truncated pyramid edge.

FIGS. 4 and 5 further illustrate that a proximal portion 33 of thedistal hub 22 may include a second stress relieving edge 35. In oneembodiment, as electrode assembly 16 moves from a delivery configuration(FIG. 4) to a deployed configuration (FIG. 5) the proximal portion 33 ofdistal hub 22 becomes the outer diameter of the deployed distal hub. Tofurther reduce the stress from the movement of the device duringdeployment, additional material from the proximal edge of the distal hubmay be removed. As an example, the space between spines may have asemicircular or arch shape, as shown in FIG. 5. So, as the innerdiameter of the distal hub decreases during expansion of the flexiblewires 28, the outer diameter of the proximal portion 33 of the hubincreases. Removal of the outer diameter material between the flexiblewires 28 will further reduce the stress during this process. In anotherembodiment, the distal hub 22 of the flexible wire assembly 29 may beannealed to increase flexibility. The increase in flexibility mayfurther reduce the stress on the distal hub as it transitions into thedeployed configuration.

The geometry of the flexible wire assembly 29 also reduces the stresscaused by the manufacturing process. Heat treatment of the flexible wireassembly 29, once the device is formed into the basket-shape, creates aheat-treatment stress. This stress is reduced due to the geometry of thedistal hub 22. At body temperature, nitinol wire is flexible and elasticand, like most metals, nitinol wires deform when subjected to minimalforce and return to their shape in the absence of that force. Nitinolbelongs to a class of materials called Shaped Memory Alloys (SMA) thathave interesting mechanical properties beyond flexibility andelasticity, including shape memory and superelasticity which allownitinol to have a “memorized shape”, (e.g. the basket-shape), that isdependent on its temperature phases. The austenite phase is nitinol'sstronger, higher-temperature phase, with a simple cubic crystallinestructure. Superelastic behavior occurs in this phase (over a 50°−60° C.temperature spread). FIG. 5 illustrates the flexible wire assembly 29 inthe “memorized shape” or basket-shape. During manufacture, the nitinoltube (FIG. 4) is heated and formed into the basket-shape. This shape isthen heat set, as is known in the art. Correspondingly, the martensitephase is a relatively weaker, lower-temperature phase with a twinnedcrystalline structure. When a nitinol material is in the martensitephase, it is relatively easily deformed and will remain deformed.However, when heated above its austenite transition temperature, thenitinol material will return to its pre-deformed shape, producing the“shape memory” effect. The temperature at which nitinol starts totransform to austenite upon heating is referred to as the “As”temperature. The temperature at which nitinol has finished transformingto austenite upon heating is referred to as the “Af” temperature.Accordingly, the basket-shaped electrode assembly 16 may have a threedimensional shape that can be easily collapsed to be fed into a guidingsheath and then readily returned to its expanded shape memoryconfiguration upon delivery to the desired region of the patient uponremoval of the guiding sheath.

FIGS. 4 and 5 illustrate a device cut from a single nitinol tube. Inother embodiments, the flexible wire assembly 29 is manufactured from asheet of nitinol material, shaped and heat set into the desired“memorized” shape.

Referring now to FIGS. 6 and 7, FIG. 6 illustrates a distal portion of aflexible wire assembly 29 in an unexpanded relaxed state. In this state,there is no stress or strain on the device since it is still in anatural tube shape. FIG. 7 illustrates the same distal portion of theflexible wire assembly 29 in an expanded shape. As the flexible wires 28move outwardly, as indicated by arrows 80, stress is concentrated at thedistal hub 22. In an example, as flexible wires 28 a and 28 b expand,the stress is concentrated at a peak, indicated by circle 82, as thepeak is forced into a smaller space. In this example, for each pair ofadjacent flexible wires, the stress is concentrated at the peak wherethe flexible wires join the distal hub. The concentrated stress in thedistal hub may be reduced by the various distal hub designs describedbelow and illustrated in FIGS. 8a to 15.

FIG. 8a illustrates another embodiment of a flexible wire assembly 29 ain an unexpanded state. In one embodiment to reduce the stress on distalhub 22 a, the distal hub may include areas of increased thickness toincrease the rigidity of the distal hub. FIG. 8b illustrates across-section of a flexible wire 28 a and a portion of distal hub 22 ataken along line A-A of FIG. 8a . In this embodiment, the portion ofdistal hub 22 a that extends above flexible wire 22 a has an increasedthickness (t1) as compared to the thickness of the flexible wire (t2).In this embodiment, the thickness (t1) of the distal hub 22 a tapersproximally along distance (d) from the distal edge of distal hub 22 atoward the distal end of flexible wire 28 a. This increase in thicknessmay be included in the entire distal hub 22 a or just a portion ofdistal hub 22 a. For example, the increased thickness (t1) may belimited to the areas of the distal hub between adjacent flexible wires,the peaks (indicated by “P”), or it may be limited to the areas of thedistal hub extending from the flexible wire, the valley (indicated by“V”). FIG. 8c illustrates another embodiment of distal hub 22 b havingan increased thickness as well as being slightly curved inward. In otherembodiments, the distal hub may only include an inward curve without theadded thickness. In these embodiments, the inward curving distal hubforms a radius of curvature that may further reduce the dimensions ofthe deployed distal hub as well as reduce any trauma to the tissue thedevice may come into contact.

FIG. 9 to FIG. 15 each illustrate various geometries of the distal hubthat may also reduce the stress on the distal hub as it moves from thedelivery configuration to the deployed configuration. In each of theseembodiments, the distal hub 22 and/or the flexible wires 28 areconfigured to reduce the stress that is transferred from the flexiblewires 28 to the distal hub 22 when the flexible wires are expanded.

FIG. 9 illustrates another embodiment of flexible wire assembly 29 chaving a distal hub 22 c with a reduced stress configuration. In thisembodiment, distal hub 22 c includes a first stress-relieving edge 31 chaving a waveform or scalloped shape, as described above. Additionally,distal hub 22 c also includes a second stress-relieving edge 35 c. Inthis embodiment, the second stress relieving edge includes reconfiguredflexible wire junctions with the distal hub 22 c. Flexible wire assembly29 c comprises a plurality of flexible wires 28 c, each having a mainbody portion including a first width (w1) and a bridge portion (bridge)84 c having a decreased width (w2) where the flexible wire 28 c joinsthe distal hub 22 c. In this embodiment, mechanical stress on the distalhub 22 c is decreased due to the reduction of width of the flexiblewires to w2 where they join the distal hub. It was found that thereduction of stress on the hub improves the overall robustness of theflexible wire assembly.

FIG. 10 illustrates another embodiment of a flexible wire assembly 29 dhaving a distal hub 22 d with a reduced stress configuration. In thisembodiment, distal hub 22 d includes a first stress-relieving edge 31 dhaving a waveform or scalloped shape, as described above. Distal hub 22d further includes another configuration of a second stress-relievingedge 35 d. In this embodiment, the second stress relieving edge includesreconfigured flexible wire junctions with the distal hub 22 d. In thisembodiment, each pair of flexible wires, e.g. flexible wires 28 d 1 and28 d 2, joins the distal hub 22 d via a bridge 84 d. In this embodiment,the nitinol tube is cut in such a way as to reduce the number offlexible wires 28 d that join the distal hub 22 d. For example, in aflexible wire assembly having twelve flexible wires, six bridges areformed to connect these wires to the distal hub 22 d. By reducing theoverall number of connections to the distal hub, there is a reduction ofmechanical stress on the distal hub. Additionally, in this embodiment,the second stress relieving edge may include a scalloped or waveformpattern, as described above, for additional reduction in stress load. Tofurther reduce the stress on the distal hub 22 d, the flexible wires 28d may include an indentation 86 d. This indentation 86 d is located atthe junction where each pair of wires joins together. This indentation86 d is formed from removing material from between the flexible wires,which allows the wires to expand more freely when moving from a deliveryconfiguration to a deployed configuration. The reduction of stress atthis point of the flexible wire assembly 28 d further reduces the stresson the distal hub 22 d.

FIG. 11 illustrates another embodiment of a flexible wire assembly 29 ehaving a distal hub 22 e with a reduced stress configuration. In thisembodiment, the bridge 84 e joining the distal hub 22 e with a pair offlexible wires 28 e comprises a sinusoid shape as compared to the linearshape of bridge 84 d of FIG. 10. In all other aspects, this embodimentis the same as that described above for FIG. 10.

FIGS. 12a and 12b illustrate another embodiment of flexible wireassembly 29 f having a distal hub 22 f with a reduced stressconfiguration. In this embodiment, distal hub 22 f includes a firststress-relieving edge 31 f having a waveform or scalloped shape. FIG.12a illustrates flexible wire assembly 29 f in a delivery configurationand FIG. 12b illustrates flexible wire assembly 29 f in a deployedconfiguration. As shown in FIG. 12a , distal hub 22 f is configured toinclude a waveform edge having “U”-shaped indentations 88 f locatedbetween each pair of adjacent flexible wires 28 f. U-shaped indentation88 f has a gap having a first distance D1 in a delivery configurationand a second distance D2 in a deployed configuration. In thisembodiment, as the flexible wires 28 f are expanded during deployment,the gap of the U-shaped indentation reduces from D1 to D2. It is thischange in formation of the U-shaped indentation that absorbs the stresscaused by the expansion of the flexible wire assembly. FIGS. 13a and 13billustrate another embodiment of flexible wire assembly 29 g having adistal hub 22 g with a reduced stress configuration similar to that ofFIGS. 12a and 12b . However, in this embodiment, the indentation 88 g ismore of a sinusoidal configuration. In all other aspects, the flexiblewire assembly 29 g is similar as that described above for FIGS. 12a and12 b.

FIG. 14 illustrates another embodiment of flexible wire assembly 29 hhaving a distal hub 22 h with a reduced stress configuration. In thisembodiment, distal hub 22 h includes a first stress-relieving edge 31 hhaving a continuous ribbon-like waveform shape. In this embodiment, thewaveform extends distally from the distal ends of the flexible wires 28h. The ribbon shaped distal hub 22 h form a plurality of distalindentations 88 h that alternate with a plurality of proximalindentations 90 h. Distal indentations 88 h have a gap distance D1 thatreduces in dimension as the flexible wire assembly is deployed. Proximalindentations 90 h have a gap distance D2 that increases in dimension asthe flexible wire assembly is deployed. In this embodiment, the ribbonshaped distal hub 22 h absorbs the stress when the flexible wireassembly transitions from a delivery configuration to a deployedconfiguration.

FIG. 15 illustrates another embodiment of a flexible wire assembly 29 ihaving a distal hub 22 i with a reduced stress configuration. In thisembodiment, distal hub 22 i includes a first stress-relieving edge 31 ihaving a generally waveform or scalloped shape and a secondstress-relieving edge 35 i having an arch-shaped configuration, asdescribed above. In addition, the distal hub 22 h further includes aplurality of distal projections 92 i. The number of distal projectionsmay vary. FIG. 15 illustrates four distal projections, but there may beas few as two and as many as eight. In this embodiment, the distalprojections 92 i are evenly distributed around the circumference ofdistal hub 22 i. In a delivery configuration, these distal projections92 i extend distally from the distal end of the flexible wire assembly.In the deployed state, these distal projections rotate inwardly as thedistal hub rotates inwardly, as described above. In the embodimentillustrated in FIG. 15, there are shown four distal projections 92 i,one for each group of three flexible wires 28 i. One with ordinary skillin the art will recognize that the number and position may varydepending on the application and the total number of flexible wires.

One of ordinary skill in the art will appreciate that elements of eachof the embodiments described above for FIGS. 3 to 15 may be combinedwith other elements from other embodiments and these combinations arewithin the scope of the invention. For example, the stress relievingedge 31 d of the distal hub 22 d illustrated in FIG. 10 may furtherinclude the inward curve of 22 b to further reduce the distal hubprofile in the deployed configuration. The following discussion of FIGS.16 to 17 also applies to each of the above described embodiments.

In a further aspect, each spine 18 may include cabling 40 with built-inor embedded lead wires 42 for the electrodes 20 carried by the spine asshown in FIGS. 16A-C. The cabling has a core 44, and a plurality ofgenerally similar wires 42 each covered by an insulating layer 46 thatenables each wire to be formed and to function as a conductor 48. Thecore 44 provides a lumen 50 in which can pass other components such as asupport structure in the form of flexible wire 28 and/or additional leadwire(s), cables, tubing or other components.

In the following description, generally similar components associatedwith cabling 40 are referred to generically by their identifyingcomponent numeral, and are differentiated from each other, as necessary,by appending a letter A, B, . . . to the numeral. Thus, wire 42C isformed as conductor 48C covered by insulating layer 46C. Whileembodiments of the cabling may be implemented with substantially anyplurality of wires 42 in the cabling, for clarity and simplicity in thefollowing description cabling 40 is assumed to comprise N wires 42A,42B, 42C, . . . 42N, where N equals at least the number of ringelectrodes on each respective spine 18 of the basket-shaped electrodeassembly 16. For purposes of illustration, insulating layers 46 of wires42 have been drawn as having approximately the same dimensions asconductors 48. In practice, the insulating layer is typicallyapproximately one-tenth the diameter of the wire.

The wires 42 are formed over an internal core 44, which is typicallyshaped as a cylindrical tube. The core material is typically selected tobe a thermoplastic elastomer such as a polyether block amide or PEBAX®.Wires 42 are formed on an outer surface 52 of the core 44 by coiling thewires around the tube. In coiling wires 42 on the surface 52, the wiresare arranged so that they contact each other in a “close-packed”configuration. Thus, in the case that core 44 is cylindrical; each wire42 on the outer surface is in the form of a helical coil, configured ina multi-start thread configuration. For example, in the case of the Nwires 42 assumed herein, wires 42 are arranged in an N-start threadconfiguration around core 44.

In contrast to a braid, all helical coils of wires 42 herein have thesame handedness (direction of coiling). Moreover, wires in braidssurrounding a cylinder are interleaved, so are not in the form ofhelices. Because of the non-helical nature of the wires in braids, evenbraid wires with the same handedness do not have a threaded form, letalone a multi-start thread configuration. Furthermore, because of thelack of interleaving in arrangements of wires in embodiments of thecabling, the overall diameter of the cabling produced is less than thatof cabling using a braid, and the reduced diameter is particularlybeneficial when the cabling is used for a catheter.

Once wires 42 have been formed in the multi-start thread configurationdescribed above, the wires are covered with a protective sheath, such asin the form of the non-conductive covering 30 described above. Theprotective sheath material is typically selected to be a thermoplasticelastomer such as for example, 55D PEBAX without additives so that it istransparent. In that regard, the insulating layer 46 of at least one ofwires 42 may be colored differently from the colors of the remainingwires as an aid in identifying and distinguishing the different wires.

The process of coiling wires 42 around the core 44, and then coveringthe wires by the non-conductive covering 30 essentially embeds the wireswithin a wall of cabling 40, the wall comprising the core and thesheath. Embedding the wires within a wall means that the wires are notsubject to mechanical damage when the cabling is used to form acatheter. Mechanical damage is prevalent for small wires, such as 48AWGwires, if the wires are left loose during assembly of a catheter.

In use as a catheter, an approximately cylindrical volume or lumen 50enclosed by the core 44, that is afforded by embedding smaller wires(such as the 48 AWG wires) in the wall, allows at least a portion of thelumen 50 to be used for other components. It is understood that theplurality of wires 42 shown in the drawings is representative only andthat a suitable cabling provides at least a plurality of wires equal toor greater than the plurality of ring electrodes mounted on each cablingor spine of the assembly. Cabling suitable for use with the presentinvention is described in U.S. application Ser. No. 13/860,921, filedApr. 11, 2013, entitled HIGH DENSITY ELECTRODE STRUCTURE, and U.S.application Ser. No. 14/063,477, filed Oct. 25, 2013, entitledCONNECTION OF ELECTRODES TO WIRES COILED ON A CORE, the entiredisclosures of which have been incorporated above. Each cabling 40 (withembedded lead wires 42) may extend to the control handle 14 for suitableelectrical connection of wires 42, thereby allowing signals measured byelectrodes 20 to be detected.

As noted, each spine 18 and cabling 40 pair carries a plurality of ringelectrodes 20, which may be configured as monopolar or bipolar, as knownin the art. Cabling 40 is schematically shown by a top view in FIG. 16Aand by a side view in FIG. 16C, in which portions of non-conductivecovering 30 have been cut away to expose wires 42 of the cabling 40, aswell as to illustrate the attachment of a ring electrode 20 to thecabling 40. FIG. 16A illustrates cabling 40 prior to attachment ofelectrode 20, while FIG. 16C illustrates the cabling after the ringelectrode has been attached. The ring electrodes 20 may have suitabledimensions to allow them to be slid over sheath 54.

The attachment point for each electrode 20 may be positioned over one ormore of the wires 42, such as wire 42E in the illustrated example. Asection of non-conductive covering 30 above the wire 42E and acorresponding section of insulating layer 46E are removed to provide apassage 54 to conductor 48E. In a disclosed embodiment, conductivecement 56 may be fed into the passage, ring electrode 20 may then beslid into contact with the cement, and finally the electrode may becrimped in place. Alternatively, the ring electrode 20 may be attachedto a specific wire 42 by pulling the wire through non-conductivecovering 30, and resistance welding or soldering the ring electrode tothe wire.

In another embodiment, basket-shaped electrode assembly may include anexpander. The expander (not shown) may comprise a wire or hypotubeformed from a suitable shape memory material, such as a nickel titaniumalloy. As will be appreciated, different relative amounts of movement ofthe expander 22 along the longitudinal axis may affect the degree ofbowing, such as to enable the spines 18 to exert greater pressure on theatrial tissue for better contact between the tissue and the electrodeson the spines. Thus, a user can change the shape of the electrodeassembly by adjusting the longitudinal extension or withdrawal of theexpander.

To help illustrate use of the basket-shaped electrode assembly 16, FIG.17 is a schematic depiction of an invasive medical procedure, accordingto an embodiment of the present invention. Catheter 10, with thebasket-shaped electrode assembly 16 (not shown in this view) at thedistal end may have a connector 60 at the proximal end for coupling thewires 42 from their respective electrodes 20 (neither shown in thisview) to a console 62 for recording and analyzing the signals theydetect. An electrophysiologist 64 may insert the catheter 10 into apatient 66 in order to acquire electropotential signals from the heart68 of the patient. The professional uses the control handle 14 attachedto the catheter in order to perform the insertion. Console 62 mayinclude a processing unit 70 which analyzes the received signals, andwhich may present results of the analysis on a display 72 attached tothe console. The results are typically in the form of a map, numericaldisplays, and/or graphs derived from the signals. With the inventivecatheter, the map from the basket-shaped electrode assembly 16 isimproved due to the reduction in the distal hub 22 dimensions, allowingmore of the electrodes to contact the chamber.

In a further aspect, the processing unit 70 may also receive signalsfrom one or more location sensors 74 provided near a distal end of thecatheter 10 adjacent the basket-shaped electrode assembly 16 asschematically indicated in FIG. 1. The sensor(s) may each comprise amagnetic-field-responsive coil or a plurality of such coils. Using aplurality of coils enables six-dimensional position and orientationcoordinates to be determined. The sensors may therefore generateelectrical position signals in response to the magnetic fields fromexternal coils, thereby enabling processor 70 to determine the position,(e.g., the location and orientation) of the distal end of catheter 10within the heart cavity. The electrophysiologist may then view theposition of the basket-shaped electrode assembly 16 on an image thepatient's heart on the display 72. By way of example, this method ofposition sensing may be implemented using the CARTO™ system, produced byBiosense Webster Inc. (Diamond Bar, Calif.) and is described in detailin U.S. Pat. Nos. 5,391,199, 6,690,963, 6,484,118, 6,239,724, 6,618,612and 6,332,089, in PCT Patent Publication WO 96/05768, and in U.S. PatentApplication Publications 2002/0065455 A1, 2003/0120150 A1 and2004/0068178 A1, whose disclosures are all incorporated herein byreference. As will be appreciated, other location sensing techniques mayalso be employed. If desired, at least two location sensors may bepositioned proximally and distally of the basket-shaped electrodeassembly 16. The coordinates of the distal sensor relative to theproximal sensor may be determined and, with other known informationpertaining to the curvature of the spines 18 of the basket-shapedelectrode assembly 16, used to find the positions of each of theelectrodes 20.

The preceding description has been presented with reference to presentlydisclosed embodiments of the invention. Workers skilled in the art andtechnology to which this invention pertains will appreciate thatalterations and changes in the described structure may be practicedwithout meaningfully departing from the principal, spirit and scope ofthis invention. As understood by one of ordinary skill in the art, thedrawings are not necessarily to scale. Accordingly, the foregoingdescription should not be read as pertaining only to the precisestructures described and illustrated in the accompanying drawings, butrather should be read consistent with and as support to the followingclaims which are to have their fullest and fair scope.

1. A catheter comprising: an elongated catheter body extending along alongitudinal axis, the elongated catheter body having a proximal end anda distal end; a flexible wire assembly positioned at the distal end ofthe elongated catheter body formed from a single piece of shape memorymaterial, the flexible wire assembly having a plurality of flexiblewires, each flexible wire having a proximal end and a distal end, theflexible wire assembly further having a distal hub extending from thedistal ends of at least a portion of the plurality of flexible wires,the distal hub configured to be generally parallel to the longitudinalaxis of the elongated catheter body when the catheter is in a firstoperational state and generally perpendicular to the longitudinal axisof the elongated catheter body when the catheter is in a secondoperational state; a plurality of spines formed from the plurality offlexible wires; and a plurality of electrodes and cabling attached toeach spine, the plurality of electrodes and cabling having acorresponding plurality of wires coiled on a core and covered by asheath such that each electrode is attached through the sheath to one ofthe plurality of wires, such that spines bow radially outwardly in thesecond operational state and are arranged generally along thelongitudinal axis of the catheter body in the first operational state.2. The catheter of claim 1, wherein the distal hub further comprises astress-relieving edge.
 3. The catheter of claim 1, wherein at least aportion of the shape memory material of the stress-relieving edgecomprises a first thickness at a distal end and tapering to a secondthickness at the distal end of the flexible wire.
 4. The catheter ofclaim 1, wherein the stress-relieving edge further includes a radius ofcurvature, the radius of curvature directed toward an inner diameter ofthe distal hub.
 5. The catheter of claim 1, wherein each of theplurality of flexible wires further comprises a bridge portion, thebridge portion connecting the distal end of the flexible wires to thedistal hub.
 6. The catheter of claim 1, wherein the distal ends of twoadjacent flexible wires form a bridge portion, the bridge portionconnecting the flexible wires to the distal hub.
 7. The catheter ofclaim 6, wherein the bridge portion comprises a sinusoid shape.
 8. Thecatheter of claim 6, wherein the bridge portion comprises a linearshape.
 9. The catheter of claim 1, wherein the distal hub comprises awaveform, the wave form further comprising a plurality of U-shapedindentations, wherein each U-shaped indentation is placed betweenadjacent flexible wires.
 10. The catheter of claim 9, wherein theU-shaped indentations define a gap, the gap having a first distance whenin the delivery configuration and a second distance when in the deployedconfiguration.
 11. The catheter of claim 1, wherein the distal hubcomprises a waveform, the wave form further comprising a plurality ofsinusoidal-shaped indentations, wherein each sinusoidal-shapedindentation is placed between adjacent flexible wires.
 12. The catheterof claim 11, wherein the sinusoidal-shaped indentations define a gap,the gap having a first distance when in the delivery configuration and asecond distance when in the deployed configuration.
 13. The catheter ofclaim 1, wherein the distal hub comprises a continuous ribbon shapedwaveform, the wave form further comprising a plurality of distalindentations, wherein each distal indentation is placed between adjacentflexible wires and extends distally from the distal ends of the flexiblewires.
 14. The catheter of claim 13, wherein the distal hub has aplurality of distal indentations that are distally oriented and aplurality of proximal indentations that are proximally oriented, whereinthe distal indentations and proximal indentations alternate and areevenly spaced around a circumference of the distal hub.
 15. The catheterof claim 1, wherein the distal hub has a first stress relieving edge anda second stress relieving edge, wherein the first stress relieving edgehas a waveform shape on a distal end of the distal hub, and the secondstress relieving edge has an arched shape on a proximal edge of thedistal hub, the distal hub further comprising at least two distalprojections, wherein the distal projections are evenly distributedaround a circumference of the distal hub.
 16. A method for forming acatheter comprising: forming an elongate catheter body; forming aflexible wire assembly from a single piece of shape memory material, theflexible wire assembly having a plurality of flexible wires joined at adistal hub; forming a stress-relieving edge onto a distal end of thedistal hub at a location opposite of the plurality of flexible wires;heating the flexible wire assembly to heat set a basket-shapedarrangement; connecting a plurality of electrodes and cabling to each ofthe plurality of flexible wires to form a basket-shaped electrodeassembly; and connecting the basket shaped electrode assembly to adistal end of the elongate catheter body.
 17. The method of claim 16,wherein the single piece of shape memory material comprises a nitinolalloy tube.
 18. The method of claim 16, wherein the stress relievingedge comprises a bridge portion connecting the flexible wires to thedistal hub.
 19. The method of claim 16, wherein the stress relievingedge comprises a continuous waveform, the continuous waveform having aplurality of indentations.
 20. The method of claim 16, wherein thestress-relieving edge comprises a plurality of distal projections.
 21. Acatheter comprising: an elongated catheter body extending along alongitudinal axis, the elongated catheter body having a proximal end anda distal end; a flexible wire assembly positioned at the distal end ofthe elongated catheter body formed from a single piece of shape memorymaterial, the flexible wire assembly having a plurality of flexiblewires, each flexible wire having a proximal end and a distal end, theflexible wire assembly further having a distal hub extending from thedistal ends of at least a portion of the plurality of flexible wires,the distal hub configured to be generally parallel to the longitudinalaxis of the elongated catheter body when the catheter is in a firstoperational state and generally perpendicular to the longitudinal axisof the elongated catheter body when the catheter is in a secondoperational state, wherein the distal hub further comprises astress-relieving edge and wherein the stress relieving edge has a firstdiameter in the first operational state and a second diameter in thesecond operational state, the first diameter being greater than thesecond; a plurality of spines formed from the plurality of flexiblewires; and a plurality of electrodes and cabling attached to each spine,the plurality of electrodes and cabling having a corresponding pluralityof wires coiled on a core and covered by a sheath such that eachelectrode is attached through the sheath to one of the plurality ofwires, such that spines bow radially outwardly in the second operationalstate and are arranged generally along the longitudinal axis of thecatheter body in the first operational state.